1, 2. Orderly, methodical, systematic characterize that which is neat, in order, and planned. These three words are sometimes used interchangeably. However, orderly emphasizes neatness of arrangement: an orderly array of books.Methodical suggests a logical plan, a definite order of actions or method from beginning to end: a methodical examination.Systematic suggests thoroughness, an extensive and detailed plan, together with regularity of action: a systematic review.

"military attendant who carries orders," 1781, short for orderly corporal, etc. Extended 1809 to an attendant at a hospital (originally a military hospital) charged with keeping things in order and clean. See orderly (adj.).